The purpose of this project was to investigate in vitro induction of cell mediated immunity, i.e., cell mediated lympholysis (CML) and mixed lymphocyte reactivity (MLR) of murine lymphocytes to syngeneic and allogeneic lymphoid cells (normal and neoplastic) modified with trinitrophenol (TNP). This study was designed to establish: a) whether the immune reactivity obtained was specific for the haptenic moiety (TNP) or whether it involved reactivity to some TNP-modified cell surface protein(s); b) whether response potential in this model was associated with an immune response (Ir) gene, and if so to determine the linkage pattern; c) how specific the reactivity is vis a vis the genetic and cellular components of the induction and effector phases; d) if the immune reaction is composed exclusively of T cells or if B cells are also required; and e) whether antibodies specific for TNP are generated in addition to the cell mediated response during the course of immunization.